For users of digital cameras, file compression is an issue you must be aware of if you want to be able to view and share your images.
If you put in the time and effort of taking a good photograph, wouldn’t you want the captured image to be as good as it can be? File compression can impact on your photos. And while the number of photos you can get on your storage media (be it compact flash, smartmedia, or numerous others) can be very tempting when you have it set to high compression, to get the best out of your photos you will need to sacrifice the small file size of highly compressed images for the better quality of lower compression.
When you take a photo with your digital camera, the camera stores it as a file on your camera’s storage medium.
Most digital cameras allow the userd to choose the file type the images are stored as. Most cameras include at least two types of JPEG files – high-compression & low-compression, and some allow you to save the files as TIFF or RAW files as well. The major difference between the file types is how much, if any, they compress the data in your image – and this will determine the quality of your images.
When you take images as TIFF or RAW files, the data are not compressed at all, or are stored using “lossless” compression. This means that, when you open the file in your photo editing or viewing program, all the information that was originally recorded by the camera is still there. So while the files are much larger than corresponding JPEG files, the photos you can print will be of a much higher quality.
The data in JPEG files are compressed when you create a file. JPEG files use a “lossy” form of compression, which means that in exchange for a small file size (and room for more photos on your camera’s storage card), some of the information recorded by the camera is lost. The amount of compression is determined by your camera’s manufacturer. A high-compression JPEG file is much smaller than a low- compression JPEG file, but more information is lost from the original image, and more artifacts from the file compression can be seen in the photo. So, the more a file is compressed, the more likely you are to see the annoying jagged lines disrupting your image.
For example – with my Nikon 775 camera – I have three choices for the file type or image quality setting. All three are JPEG files – a low-compression mode (Fine mode), a medium-compression mode (Normal mode) and a high-compression mode (Basic mode). The files taken in Fine mode are about four times as large as the ones created in Basic mode. The smaller files have been compressed much more than the larger ones – and are much more likely to show lines and pixels that have been affected by the file compression.
You may not be able to see the differences in the images on the viewscreen on your camera. But they will become visible on your computer monitor, and especially when you print your pictures.
So if you want to avoid the little jagged lines and other artifacts of JPEG compression in your images – the first thing you should do is check the settings in your camera. Set the file quality for the highest quality you can -either a low-compression JPEG file or even better a non-compressed file type such as TIFF or RAW.
Combining no- or low-compression with using the largest resolution your camera allows will give you the largest image files your camera can produce, which will give you more data to work with when you edit your images. If all you are doing is making small images for the web, these factors will not matter much, but if you plan on enlarging or printing, then the camera’s resolution and file compression settings will be important. The end result will be better images that you can enlarge without having to worry as much about loss of image quality.
Examples showing the impact of file compression on images can be found at:
http://www.hankinslawrenceimages.com/newsletter/articles/ jpg_camera.htm
Patty Hankins & Bill Lawrence publish HLI Photonotes, their monthly ezine, which provides information and tips for photographers. To subscribe email hl_images@earthlink.net with subscribe in the subject or visit www.hankinslawrenceimages.com.
